Many
microorganisms show gravitaxis, including
Euglena. King crab
planktonic larvae (
Lithodes aequispinus) show negative gravitaxis, but positive
phototaxis. The
larval stages of a number of trematodes parasites also show gravitaxis. This gravitaxis helps them locate hosts in the
water column. They can either show positive, or negative gravitaxis, depending on the type of host species. ==Etymology==